The Principal Investigator (PI) is a full time academic neurosurgeon who specializes in surgery of the posterior fossa for neurovascular compression syndromes. This research career award will afford him the time to acquire the skills needed to perform further patient-oriented research in neurogenic hypertension and obtain a Master of Science degree in Clinical Research. The research and training experience he will obtain during the period of the K23 Award will allow him to become an independent clinical investigator with a focus on mechanisms of neurogenic hypertension, and to be able to design and conduct studies on its therapy. The PI has the commitment and support of his sponsor, department and institution to permit the time and allocate the resources needed to attain his research career goals and complete his proposed research. Training will be facilitated through the institutions K30 Award and a NIH supported GCRC. The hypothesis to be tested is that neurogenically mediated hypertension is caused by arterial compression of areas along the retro-olivary sulcus of the ventro-lateral medulla. Therefore the aims of the project are to: 1) electrically establish in humans the locations along the normal surface of the ventro-lateral medulla that are sensitive to stimulation and produce pressor responses; and 2) show an association between arterial compression of these 'pressor-sensitive' areas along the medullary surface (established in Aim 1) and aberrations in sympathetic tone and cardiovascular functions in volunteering subjects with neurogenic hypertension. Hemodynamic and sympathetic response patterns to electrical stimulation of the medullary surface will be recorded to map the location of the pressor-regulating neuronal groups under the surface of the ventro-lateral medulla in patients undergoing surgery of the posterior fossa. This information on response patterns will then be used in a second study to investigate associations between arterial compression of these pressor-regulating areas and similar measured patterns in hypertensive individuals. Results from this research should help to better define the physiologic criteria to be used to relate arterial compression of the ventro-lateral medulla to neurogenic hypertension.